Some of this may seem obvious, but it is worth checking that the surrounding area suits your needs:

Accessibility

Commute time and transport links to work

Local amenities

Proximity to key places, distance from shops, venues for socialising, sports facilities etc.

Suitability to your lifestyle

Is it a happening place?  What is the neighbourhood like?  Are there children or elderly people living close by?

Safety

How safe does the area feel?  Would you be confident walking around in the dark?

Surrounding area

What is nearby?
Are there any potential hazards or nuisance factors e.g. smells, pollution, pylons, mobile phone mast etc.?
If it is close to water, check if it has ever been flooded.
Do ask if there is anything you are concerned about e.g. what are those building works close by?

Traffic/noise

Proximity to likely sources of traffic or noise e.g. busy road, railway, flight path, schools, places of worship, building sites, barking dogs.  Revisit the property at a time when you can experience the full impact.
An agent/landlord is obligated to inform you at the viewing, if not before, about potential nuisances such as a tube running under the property, whether or not you can hear it.
 
 

Parking

Check parking facilities – permits, car park, parking on property?  
How many allocated spaces?
What is the cost?